swift 3

swizzlingExample.swift

extension UINavigationController {
    open override class func initialize() {
        if self != UINavigationController.self { return }
        
        let swizzlingClosure: () = {
           UINavigationController().swizzlePushViewController()
        }()
        swizzlingClosure
    }
    
    private func swizzlePushViewController() {
        let originalSelector = #selector(UINavigationController.pushViewController(_:animated:))
        let swizzledSelector = #selector(UINavigationController.ai_pushViewController(_:animated:))
        let originalMethod = class_getInstanceMethod(UINavigationController.self, originalSelector)
        let swizzledMethod = class_getInstanceMethod(UINavigationController.self, swizzledSelector)
        
        let flag = class_addMethod(UINavigationController.self,
                                   originalSelector,
                                   method_getImplementation(swizzledMethod),
                                   method_getTypeEncoding(swizzledMethod))
        
        if flag {
            class_replaceMethod(UINavigationController.self,
                                swizzledSelector,
                                method_getImplementation(originalMethod),
                                method_getTypeEncoding(originalMethod))
        } else {
            method_exchangeImplementations(originalMethod, swizzledMethod)
        }
    }
    
    @objc private func ai_pushViewController(_ viewController: UIViewController, animated: Bool) {
        print(viewController)
        self.ai_pushViewController(viewController, animated: animated)
    }
}